feat: per-tool settings, persistent settings file, Codex and Antigravity sessions, tokens and hooks (#40 B, C1, C2, D)

Part B: Model Pricing, Hook Configuration and CLAUDE_HOME move from
Settings → Dashboard to the Claude Code tab's AgentHub sub-tab
(ClaudeAgentHubSettings.tsx); CODEX_HOME is editable in Codex → AgentHub.
A home that is or contains the OS home is refused (EBADHOME).

Settings persistence: dashboard-saved settings go to
~/.config/agenthub/settings.env (AGENTHUB_SETTINGS_FILE), outside the plugin
cache an update wipes. Load order: real env > the checkout's .env > that file.
The first CLAUDE_HOME change pins DASHBOARD_DATA_DIR so the DB stays put.

C1: codex-usage.js reads Codex rollout journals into sessions (new column
tool) and token_usage, tracked per file in codex_rollouts; forks deduped by
total vector, sub-agent threads folded into the root; pricing-sync also
prices OpenAI models; PricingSettings with a vendor filter.

C2: codex-hooks.js installs AgentHub's hooks into $CODEX_HOME/hooks.json on
a click, through a stable forwarder; Codex trust is never written. The hook
route creates tool='codex' sessions and folds sub-agent hooks into the root.

D: antigravity-usage.js reads agy's per-conversation SQLite files (tokens
from ModelUsageStats) into tool='antigravity' sessions; antigravity-hooks.js
installs the named hook `agenthub` (PreInvocation, PostToolUse, Stop — never
PreToolUse) into ~/.gemini/config/hooks.json; Settings → Antigravity tab;
Gemini pricing.

Whole-change review fixes: sameOriginGuard on both home PUTs, routers.missing
on a CLAUDE_HOME change, reset-pricing scope, GET /api/sessions?tool=,
clear-data covering the new tables, Codex child-thread events moving no
status, hooks owning status only while current, EFOREIGN for a forwarder
that is not ours, agy quiet window and turn rules, AGENTHUB_SETTINGS_FILE
honoured from .env.

Docs, OpenAPI and the CLAUDE.md marker updated. Server 2141, client 779.

client/src/components/__tests__/SessionToolBadge.test.tsx

@@ -0,0 +1,29 @@
+/**
+ * @file SessionToolBadge.test.tsx
+ * @description The session tool chip: nothing for a Claude Code session (so
+ * every hook row renders as before), the tool's name for a Codex one.
+ * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
+ */
+
+import { render, screen } from "@testing-library/react";
+import { describe, expect, it, vi } from "vitest";
+import { SessionToolBadge } from "../SessionToolBadge";
+
+vi.mock("../../lib/api", () => ({ api: { aiTools: { list: () => new Promise(() => {}) } } }));
+
+describe("SessionToolBadge", () => {
+  it("renders nothing for a Claude or unset tool", () => {
+    const { container } = render(
+      <>
+        <SessionToolBadge tool="claude" />
+        <SessionToolBadge tool={undefined} />
+      </>
+    );
+    expect(container).toBeEmptyDOMElement();
+  });
+
+  it("names a Codex session's tool", () => {
+    render(<SessionToolBadge tool="codex" />);
+    expect(screen.getByText("Codex")).toHaveAttribute("title", "Recorded by Codex");
+  });
+});